A density increase in unexposed areas of a silver halide photographic material (hereinafter referred to as a "light-sensitive material") due to development processing is called "developer fog". This phenomenon is more likely to occur when the light-sensitive material has higher sensitivity, is preserved for a longer period of time, or under severer conditions, i.e., higher temperature and higher humidity.
Further, fog is extremely apt to occur in high-temperature rapid processing or high-activity rapid processing which is often adopted for reduction of processing time. Generation of developer fog should be minimized as it brings about deterioration of photographic properties, such as reduction in image contrast.
Conventional techniques for the inhibition of developer fog include addition of antifoggants to light-sensitive materials or a developer. A number of compounds have been proposed as antifoggants as disclosed, e.g., in Birr, Stabilization of Photographic Silver Halide Emulsions (Focal Press, 1974). However, these conventional antifoggants are disadvantageous in that they decrease sensitivity or gradation of the light-sensitive materials, or tend to interfere with the adsorption of a sensitizing dye onto silver halide grains, thus hindering color sensitization. Also, these disadvantages become more conspicuous as the activity of the antifoggants becomes higher. A compound is eagerly sought which can inhibit fog generation without impairing sensitivity and gradation or adversely affecting color sensitization.